87713989 ÷ 645 
We want to figure out the number of times 87713989 can be divided by 645.

Step 1:
645 goes into 8 0 times with a remainder of 8.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
Deduct 0 from 8 and we're left with 8.
Fetch the next digit (7) from the dividend, attach it to 8 and continue: 87 / 645

Advancing to step 2:
If we divide 87 by 645, we get 0 and a remainder of 87.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
If we subtract 0 from 87, we get 87.
Append the next digit (7) from the dividend to 87 and continue with: 877 / 645

Moving on to step 3:
877 divided by 645 is 1 with a remainder of 232.
Write down 1 as next digit of the result. 
Result so far: 1.0
Subtract 645 from 877 to get 232.
Fetch the next digit (1) from the dividend, attach it to 232 and continue: 2321 / 645

Moving on to step 4:
If we divide 2321 by 645, we get 3 and a remainder of 386.
Use 3 as the next digit of our solution. 
Result so far: 13.0
If we take 1935 away from 2321, we end up with 386.
Bring next digit (3) of the dividend behind the 386 and repeat the process: 3863 / 645

Let's proceed to step 5:
3863 divided by 645 is 5 with a remainder of 638.
Record the quotient 5 as the next digit in the result. 
Result so far: 135.0
The remainder is 638 after subtracting 3225 from 3863.
Bring next digit (9) of the dividend behind the 638 and repeat the process: 6389 / 645

Advancing to step 6:
The number 645 fits into 6389 9 times, leaving a remainder of 584.
The number 9 becomes the next digit in our result. 
Result so far: 1359.0
Subtract 5805 from 6389 to get 584.
Include the next digit (8) from the dividend after 584, then repeat: 5848 / 645

Step 7:
645 goes into 5848 9 times with a remainder of 43.
The number 9 becomes the next digit in our result. 
Result so far: 13599.0
Deduct 5805 from 5848 and we're left with 43.
Bring next digit (9) of the dividend behind the 43 and repeat the process: 439 / 645

Advancing to step 8:
When dividing 439 by 645, we get 0 with a remainder of 439.
Put 0 as the next digit of the answer. 
Result so far: 135990.0
If we subtract 0 from 439, we get 439.
Since there are no more digits in the dividend, we add a zero to the remainder making it 4390, and continue the process.

Advancing to step 9:
If we divide 4390 by 645, we get 6 and a remainder of 520.
The number 6 becomes the next digit in our result. 
Result so far: 135990.6
Subtract 3870 from 4390 to get 520.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5200, and continue the process.

Going ahead to step 10:
645 goes into 5200 8 times with a remainder of 40.
The next digit of our result is 8. 
Result so far: 135990.68
The remainder is 40 after subtracting 5160 from 5200.
Since there are no more digits in the dividend, we add a zero to the remainder making it 400, and continue the process.

Going ahead to step 11:
If we divide 400 by 645, we get 0 and a remainder of 400.
The number 0 becomes the next digit in our result. 
Result so far: 135990.68
Deduct 0 from 400 and we're left with 400.
Since there are no more digits in the dividend, we add a zero to the remainder making it 4000, and continue the process.

Advancing to step 12:
If we divide 4000 by 645, we get 6 and a remainder of 130.
Put 6 as the next digit of the answer. 
Result so far: 135990.6806
The remainder is 130 after subtracting 3870 from 4000.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1300, and continue the process.

Moving on to step 13:
1300 divided by 645 is 2 with a remainder of 10.
The number 2 becomes the next digit in our result. 
Result so far: 135990.68062
Subtracting 1290 from 1300 leaves us with 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

Step 14:
645 can be fit into 100 0 times, resulting in a remainder of 100.
Use 0 as the next digit of our solution. 
Result so far: 135990.68062
Subtracting 0 from 100 leaves us with 100.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1000, and continue the process.

Let's proceed to step 15:
If we divide 1000 by 645, we get 1 and a remainder of 355.
Put 1 as the next digit of the answer. 
Result so far: 135990.6806201
Subtract 645 from 1000 to get 355.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3550, and continue the process.

Step 16:
645 goes into 3550 5 times with a remainder of 325.
Put 5 as the next digit of the answer. 
Result so far: 135990.68062015
If we take 3225 away from 3550, we end up with 325.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3250, and continue the process.

After the division, we end up with 135990.68062015 and a remainder of 3.25e-07.